Restore ResetAndPrewarm as a deprecated shim

[sdatkinson]

Summary

Adds a temporary DSP::ResetAndPrewarm() compatibility shim on top of the new Reset() prewarm controls.

Reset() now prewarms by default and can be controlled with SetPrewarmOnReset(). This PR restores the old explicit ResetAndPrewarm() API as a deprecated helper so downstream callers have a migration path before removal in v0.6.0.

Changes

• Adds DSP::ResetAndPrewarm(sampleRate, maxBufferSize).
• Implements it by temporarily forcing prewarmOnReset = true, calling Reset(), then restoring the previous setting.
• Uses RAII so the previous setting is restored if Reset() throws.
• Adds tests for:
  • forcing prewarm when PrewarmOnReset is disabled
  • restoring the previous setting on exception

Testing

cmake --build build --target run_tests -j4
./build/tools/run_tests